I scrub our litterboxes with Dawn and water, then spray with vinegar, and then leave it in direct sunlight for a few hours.
I'm hesitant to use commercial cleaners on any part of my house because of the cats. I even clean my floors (vinyl and laminate, I understand some floors will not do well with this method) with a water/vinegar/Dawn solution.
I wash the kitchen floor with vinegar + water. Have done that for years! I'll continue on with Dawn + vinegar + water for the litterbox. Forget the Sal Suds.